LED (light-emitting diode) light source is a light source based on a light-emitting diode. The LED light source has a plurality of advantages, such as, supporting low-voltage power supply, low energy consumption, wide applicability, high stability, short response time, no harm upon the environment, and multi-colors light emission. With continuous development of LED technology, LED light sources have been widely used in shopping malls, factories, and housings. The LED light sources are used for lighting or decoration, and brightness of the LED light sources is adjusted according to user needs. Normally, the LED is driving by a constant current, its brightness varies with the current flow through the LED string.
Driving methods of LED light source mainly include CCM (Continuous Conduction Mode) and DCM (Discontinuous Conduction Mode). In CCM dimming, the current of an inductor does not reach zero during one switching cycle, that is, the inductor does not “reset”. Cost of the CCM dimming is high and the CCM dimming is difficult to be controlled for an inductor saturation is prone to occur. In DCM dimming, current of an inductor is properly reset during one switching cycle. The current of the inductor is zero when a power switch is turned on. In traditional DCM dimming, harmonic current is high, and there are too many factors affecting a current of a circuit. The electromagnetic interference is strong. In the case of a plurality of LED light sources are in a circuit, the LED light sources have poor consistency, resulting in a large difference between dimming effects of the LED light sources. Therefore, how to effectively adjust brightness of a light and enhance the consistency of LED light sources has become an urgent problem to be solved.